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The purpose of this SAE Recommended Practice is to describe the terms yield strength and yield point. Included are definitions for both terms and recommendations for their use and application.

The purpose of this SAE Recommended Practice is to describe the terms yield strength and yield point. Included are definitions for both terms and recommendations for their use and application.

The SAE system of designating steels, described in SAE J402, classifies and numbers them according to chemical composition. In the case of the high-strength, low-alloy steels in SAE J1392 and J1442 and the high-strength carbon and alloy die drawn steels in SAE J935, minimum mechanical property requirements have been included in the designations. In addition, hardenability data on most of the alloy steels and some of the carbon steels will be found in SAE J1268.

This SAE Information Report relates to hot-rolled steel bar products. It is intended as a guideline to assist in the selection and specification of hot-rolled steel bar; however, it is not to be interpreted as a material specification in itself.

This SAE Standard is intended to supply a uniform means of designating wrought ferrous materials reported in SAE Standards and Recommended Practices. A numerical index system is used to identify the compositions of the SAE steels. This system makes it possible to use numbers on shop drawings and blueprints to describe partially the composition of the material. A four-numeral series is usually used to designate standard alloy and carbon steels specified to chemical composition ranges. There are certain types of alloy steels which are designated by five numerals. The prefix E is used to designate steels which are made by the basic electric furnace process with special practices. The suffix H is used to designate standard hardenability steels. The last two digits of the four-numeral series and the last three digits of the five-numeral series are intended to indicate the approximate mean of the carbon range.

This SAE Standard is intended to supply a uniform means of designating wrought ferrous materials reported in SAE Standards and Recommended Practices. A numerical index system is used to identify the compositions of the SAE steels. This system makes it possible to use numbers on shop drawings and blueprints to describe partially the composition of the material. A four-numeral series is usually used to designate standard alloy and carbon steels specified to chemical composition ranges. There are certain types of alloy steels which are designated by five numerals. The prefix E is used to designate steels which are made by the basic electric furnace process with special practices. The suffix H is used to designate standard hardenability steels. The last two digits of the four-numeral series and the last three digits of the five-numeral series are intended to indicate the approximate mean of the carbon range.

Restricted hardenability steels have been in use for some time but the specific restrictions for a particular grade depend upon customer needs and vary from mill to mill. Such steels are desirable to provide more controlled heat treatment response and dimensional control for critical parts. Because of increasing interest in steels with restricted hardenability, the SAE Iron and Steel Technical Committee directed Division 8 to prepare a set of standard steels with restricted hardenability. In general, steels with restricted hardenability (RH steels) will exhibit a hardness range not greater than 5 HRC at the initial position on the end-quench hardenability bar and not greater than 65% of the hardness range for standard H-band steels (see SAE J1268) in the "inflection" region. Generally the restricted hardenability band follows the middle of the corresponding standard H-band. An example of the RH band compared with the standard H-band is given for SAE 4140 in Figure 1.

Restricted hardenability steels have been in use for some time but the specific restrictions for a particular grade depend upon customer needs and vary from mill to mill. Such steels are desirable to provide more controlled heat treatment response and dimensional control for critical parts. Because of increasing interest in steels with restricted hardenability, the SAE Iron and Steel Technical Committee directed Division 8 to prepare a set of standard steels with restricted hardenability. In 1993, the American Society for Testing and Materials (ASTM) adopted the twelve SAE restricted hardenability steels and added ten more. SAE decided to include in SAE J1868 the additional 10 steels. In general, steels with restricted hardenability (RH steels) will exhibit a hardness range not greater than 5 HRC at the initial position on the end-quench hardenability bar and not greater than 65% of the hardness range for standard H-band steels (see SAE J1268) in the "inflection" region.

Supplementary to the heat or cast analysis, a product analysis may be made on steel in the semifinished or finished form. For definitions and methods of sampling steel for product chemical analysis, refer to SAE J408. A product analysis is a chemical analysis of the semifinished or finished steel to determine conformance to the specification requirements. The range of the specified chemical composition is normally expanded to take into account deviations associated with analytical reproducibility and the heterogeneity of the steel. Individual determinations may vary from the specified heat or cast analysis ranges or limits to the extent shown in Tables 1 through 5. The several determinations of any element in a heat or cast may not vary both above and below the specified range except for lead. Tables 1 through 5 provide permissible limits for various steel forms and composition types.

This SAE Standard prescribes the procedure for making hardenability tests and recording results on shallow and medium hardening steels, but not deep hardening steels that will normally air harden. Included are procedures using the 25 mm (1 in) standard hardenability end-quench specimen for both medium and shallow hardening steels and subsize method for bars less than 32 mm (1-1/4 in) in diameter. Methods for determining case hardenability of carburized steels are given in SAE J1975. Any hardenability test made under other conditions than those given in this document will not be deemed standard and will be subject to agreement between supplier and user. Whenever check tests are made, all laboratories concerned must arrange to use the same alternate procedure with reference to test specimen and method of grinding for hardness testing.